Principal Engineer, Safety Methods (Nuclear Thermal-Hydraulics)

Location: Bellevue, Washington, United States

Salary: $168,316–$252,475 per year; range specific to Washington State.

Company

hirify.global develops advanced nuclear reactor technologies, including the Natrium reactor, and medical isotope applications.

What you will do

• Develop plant-scale thermal-hydraulic analysis methods, numerical approaches, and closure models for the Natrium reactor.
• Perform steady-state and transient system-level analyses to evaluate model behavior, method performance, and fidelity requirements.
• Create and maintain qualification plans covering numerical verification, applicability envelopes, and performance characterization.
• Formulate and integrate heat-transfer, pressure-drop, mixing, and component-level correlations into analysis frameworks.
• Build automated workflows for model setup, execution, post-processing, and repeatable method application.
• Collaborate across engineering disciplines, document methods for design and licensing support, and mentor junior engineers.

Requirements

• Degree in Mechanical, Nuclear, Chemical Engineering, or a similar field, plus 12+ years of system-level thermal-hydraulic modeling and method development experience.
• Experience developing numerical schemes, closure models, and stability and accuracy optimization strategies.
• Experience with system-level thermal-hydraulic analysis tools such as RELAP5-3D, GOTHIC, SAS, or equivalent.
• Strong knowledge of thermal-fluids, reactor system behavior, and advanced-reactor thermal-hydraulic phenomena.
• Experience with sensitivity analysis, model-gap identification, scientific programming, and workflow automation using Python or MATLAB.
• Familiarity with NQA-1 quality assurance, configuration control, model traceability, and reproducible modeling workflows; candidates must meet applicable ANSI/ANS 3.1 education and experience requirements.

Nice to have

• Relevant nuclear industry experience applicable to qualification requirements.
• Experience supporting multiple method-development efforts in parallel.

Culture & Benefits

• Medical, vision, dental, life, disability, wellness, and gender-affirmation benefits.
• 401(k) plan and eligibility for discretionary short-term incentive payments.
• 21 days of accrued paid time off and 10 paid holidays.
• Parental leave, relocation assistance, and professional and educational support.
• Travel requirement of 0–10%; work includes extended sitting and standard working conditions exceeding eight hours per day.